The economic impact of immigration is one of the most controversial and least understood public issues in contemporary Britain. Much of the public debate ignores what little evidence there is and many policymakers seem to struggle to understand the impacts of immigration, let alone optimise them.

Unprecedented levels of immigration have led to unprecedented levels of concern about the impacts on the economy and the public purse. The Bank of England grapples with wage impacts, local authorities worry about pressure on public services, the government is introducing new policies in an attempt to improve immigration's contributions to the labour market, and the Polish plumber seems to have displaced the asylum seeker as a major target of public concern. However, while debates about the economics of immigration are more sensible and legitimate than past debates about race and colour, current discussions still tend to rely on myth rather than evidence.

New research published by the Institute for Public Policy Research this week shows that on many criteria, most immigrant groups do better in economic terms than the UK-born population. As discussed last night on Channel 4's Dispatches, the average immigrant earns more, works longer hours, is better educated and makes a stronger fiscal contribution than their British-born counterpart. Even relatively low-paid immigrants make important economic contributions by staffing public services. One in two working-age Filipinos and nearly one in three Jamaicans, Nigerians and Zimbabweans work in health or social work.

Our research also reveals the immense heterogeneity between immigrant communities - another key issue neglected in public discussion. For example, seven of the 25 largest immigrant groups are half as likely as the UK-born population to be living in social housing, while seven other groups are more than twice as likely.

This heterogeneity also suggests that, despite doing better on aggregate, there are some immigrant groups that face serious socio-economic problems. These groups cannot be identified on the basis of race, as some might have us believe - for example Ugandan-born immigrants earn more on average than French-born. However, there are communities whose employment levels, benefit reliance and educational attainment are a cause for concern - these include the Bangladeshi, Pakistani, Portuguese, Somali and Turkish communities.

There are many who will see this as proof that there are some communities who are indeed a drain on society and whose members should be refused admission or even expelled.

However, this overlooks an important fact. Immigrant groups whose members tend to be admitted on the basis of economic criteria tend to have very favourable economic characteristics. On the other hand, many of the groups that frequently appear at the bottom of the rankings tend to contain high proportions of people admitted on the basis of an asylum claim, family reunion, or European Union citizenship.

All this begs the question of whether the government's new zeal to tighten up the rules governing the admission of workers from outside the EU is necessary. Indeed, the most effective way to improve the economic impact of immigration would be to apply economic criteria to the admission of other categories of entrants. Such measures would be deeply problematic in terms of the human rights of asylum seekers and foreign spouses and in terms of EU free movement rights, but left unchecked this is where the current emphasis on the economics of immigration may lead.

It is reassuring that many of Britain's immigrants make strong economic contributions, but it is critical that economic criteria should not become the sole basis on which immigrants are judged. That many refugees, foreign spouses and EU citizens exercising the treaty rights go on to contribute such a great amount to their host country's economy should be viewed as a bonus, rather than an expectation.